Broccoli cheese soup

1 head broccoli washed and cooked until tender.  Cover with just enough water. Drain some water off. But leave about 1/2 c or so of water. Use a masher to break up broccoli to desired size.
Sauté 1 med onion chopped in 2 T butter. In separate pan.  Till tender. Can add celery as well.
Add cooked onions to broccoli.
Add 4 T flour. Stir around.
Then add
1 Qt half and half
1 can cream of mushroom
4 T butter melted.
1 jar of cheese wiz

Heat thoroughly just enough to melt cheese. Stirring occasionally. Do NOT boil. Cook  On less than medium heat. U don't want it to burn.
Very good on baked potatoes.